php-event-dispatcher

Dispatch notifications using PHP callbacks

The Event_Dispatcher acts as a notification dispatch table. It is used to
notify other objects of interesting things. This information is encapsulated
in Event_Notification objects. Client objects register themselves with the
Event_Dispatcher as observers of specific notifications posted by other
objects. When an event occurs, an object posts an appropriate notification to
the Event_Dispatcher. The Event_Dispatcher dispatches a message to each
registered observer, passing the notification as the sole argument.